Learn how methotrexate went from a cancer drug to a staple treatment for rheumatoid arthritis and other types of inflammatory arthritis conditions. Facts for patients and caregivers about the SMARD drug Methotrexate (Rheumatrex, Trexall, Otrexup, Rasuvo), such as usages, common dosages, safety tips, and possible side effects. Methotrexate is a medication that treats arthritis, psoriasis and other inflammatory conditions. Learn more about its uses and side effects. Learn about the side effects of methotrexate, from common to rare, for consumers and healthcare professionals. Methotrexate, formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. It is used for cancers such as breast cancer, leukemia, lung cancer, lymphoma, gestational trophoblastic disease, and osteosarcoma, as well as autoimmune diseases such as psoriasis, rheumatoid arthritis, and Crohn's. Withhold or discontinue Methotrexate Tablets for severe renal toxicity taking into account the importance of Methotrexate Tablet treatment in the context of the severity of the disease being treated, the severity of the adverse drug reaction, and availability of alternative therapy [see Dosage and Administration (2.6)]. Find patient medical information for Methotrexate (Rheumatrex, Trexall, and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings Methotrexate is used to treat certain types of cancer and rheumatoid arthritis. Learn about side effects, drug interactions, dosages, warnings, and more. Description Methotrexate tablet is used alone or together with other medicines to treat several types of cancer, such as breast, head and neck, lung, blood (eg, acute lymphoblastic leukemia or ALL), bone, lymph node (eg, mycosis fungoides, relapsed or refractory non-Hodgkin lymphoma), or uterus cancer. Methotrexate treats certain leukemias and lymphomas, mycosis fungoides, rheumatoid arthritis, polyarticular juvenile idiopathic arthritis in children, and severe psoriasis in adults. Learn about side effects, interactions, and indications.